Abstract
The adoption of bio-based polyesters like poly(L-lactide) (PLLA) and polyhydroxyalkanoates (PHAs) is hindered by low crystallization rates, causing thermal instability and brittleness. Hydrogen-bonding oxalamide-based compounds (OXAs) have been synthesized as nucleating agents to enhance crystallization in these polymers. OXAs dissolve into the polymer matrix, self-assembling during cooling to provide surfaces for heterogeneous nucleation. The nucleation mechanisms were investigated under quiescent and flow conditions using thermal, morphological, rheological, and conformational techniques, enabling the construction of phase diagrams for two OXAs. Flash Differential Scanning Calorimetry (FSC) and small-angle X-ray scattering (SAXS) under shear conditions were pivotal in interpreting nucleation behaviors. OXAs’ nucleating ability depends on parameters like concentration, undercooling, interface, and molecular weight, suggesting surface-driven and stretch-induced rather than epitaxial nucleation. In PLA stereocrystals, epitaxial growth was observed, with mechanisms studied using wide-angle X-ray scattering (WAXS), Transmission Electron Microscopy, and Nano XRD at the European Synchrotron Radiation Facility (ESRF). Additionally, the thermostability of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has been studied and improved to mitigate degradation from biosynthesis residuals and expand their processing windows. Finally, a polyolefin system is studied with the ultimate nucleating agent (KB25) as a proof of concept, demonstrating that growth in one dimension is the most efficient.
Publications for Communication and Dissemination
| Publication topic/title | Type of publication | Status |
| Fundamental mechanism of bis-oxalamide based nucleating agents in PLA under quiescent conditions. | Journal article | Waiting for feedback |
| Fundamental mechanism of bis-oxalamide based nucleating agents in PLA under defined flow conditions. | Journal article | Writing |
| Review: Sustainable Silk Fibroin for Biomedical Applications: A Molecular Biotechnology Challenge | Journal article | Published |
| Study on PHA’s thermostability and the effect of nucleating agents. | Journal article | In preparation |
| From stretch-induced to epitaxy: difference between homocrystals and stereocrystals. | Journal article | In preparation |
| Action plans | Target actors/audience | Means | Timing |
| Training events Biobased Value Circle #3 in Netherlands | Other ESRs and supervisors within the consortium | Presenting | May, 2022 |
| Training events Biobased Value Circle #4 in Cologne | Other ESRs and supervisors within the consortium | Presenting | November, 2022 |
| Training events Biobased Value Circle #5 in Graz | Other ESRs and supervisors within the consortium | Presenting | May, 2023 |
| LinkedIn Biobased Value Circle | Academic/Industry and general public; wide range of professionals | Promotion | tbd |
| Training events Biobased Value Circle #6 in Galway | Other ESRs and supervisors within the consortium | Presenting | November 2023 |
| Final symposium Biobased Value Circle in Maastricht | Other ESRs and supervisors within the consortium | Presenting | May 2024 |
| Final symposium Biobased Value Circle in Maastricht – Auditorium | Academic/Industry and general public; wide range of professionals | Presenting | May 2024 |
| Brightlands polymer days | Scientific audience mostly with polymer science background | Presence | November 2021 |
| Chains (NL) | Scientific audience mostly with chemistry background | Poster presenting | September, 2022 |
| Dutch polymer days (NL) | Scientific audience mostly with polymer science background | Presenting | April 2023 |
| ACS Spring Conference in New Orleans (US) | Scientific audience mostly with polymer science background | Presenting | March 2024 |
Protection of the acquired intellectual property (patents applications) etc.
Based on developing knowledge ultimate design of NA to be patented.
Impact on science and/or technology
The developed analytical methods using fast chip calorimetry and nanometer spatial resolution X-Ray imaging provide decisive insight in the mechanisms of nucleation. The gained structural – and in relation chemical insights direct our pathway in designing the ultimate nucleating agent for biobased polyesters. The next mechanism is no longer entropy based and so limited to a very narrow functional window, but epitaxy controlled.
Impact on innovation (companies)
Based on the generated expertise in analytical tools, the fundamental understanding and new direction in research, the company that excels in the development and commercialization of nucleating agents contacted us to explore joint research and technology transfer. Based on epitaxy controlled nucleating agents that fosters the concept in chemical compatibilization of OXA, a generic and broadly applicable platform of nucleating agents will be developed.
Impact on society
With the development of OXA and new nucleating agents, the applicability and commercial use of biobased polyesters will be promoted with respect to the current status as disclosed in Figure 11.
Figure 11: Climate change (kg CO2 eq./kg), cradle to gate (in red) – exemplary LCA parameter
Visual Summary – Poster
